In present audio fire alarm systems, it is common to find systems that are not able to effectively utilize the power of a given size amplifier. Because of this, different manufacturers have provided fire alarm systems having various amplifier sizes, all in an attempt to find the optimal power density for a typical fire alarm application. In addition, the requirement for backup amplification in a fire alarm system often requires additional, unused amplifiers to be installed as a means of providing that backup. Both of these limitations add to the equipment cost of a typical alarm system installation.
FIG. 1 illustrates a prior art amplifier assembly, given generally as 10. The assembly 10 includes a plurality of heat sinks 14 having a plurality of amplifiers 12 mounted to each heat sink 14. Generally, the amplifier assembly 10 includes two heat sinks 14, each heat sink having two amplifiers 12 mounted thereon.
In one prior art amplifier assembly 10, two 25-watt audio amplifiers 12 are packaged onto a single 50-watt rated heat sink14. Each amplifier 12 serves a particular zone in a fire alarm system to provide audible messages during an alarm situation. In a system with three zones, for example, the amplifier assembly 10 includes two dual packages, each dual package having one heat sink 14 with the amplifiers 12 as shown in FIG. 1. Three of the amplifiers 12 are used to provide power to the three zones while the fourth amplifier within the two packages serves as a backup that can be switched over to any of the three zones in the event of failure of one of the first three audio amplifiers. Typically, each floor or zone requires about 15 watts which can be served by an individual 25-watt amplifier.
A disadvantage of the amplifier assembly 10 having two heat sinks 14, with each heat sink having two amplifiers 12, is the cost involved in manufacturing such an assembly. With a relatively high number of components within the assembly 10, the cost of manufacturing the amplifier assembly 10 is also relatively high.
In order to overcome the relatively high cost of manufacturing an amplifier assembly with multiple heat sinks and multiple amplifiers on each heat sink, an amplifier assembly can be manufactured having a single heat sink with a plurality of amplifier stages mounted to the heat sink. The amplifier assembly includes a heat sink and a plurality of amplifier stages mounted to the heat sink. The heat sink includes a heat sink power rating and each amplifier stage has a power rating. The power rating of each amplifier stage is approximately equal to the power rating of the heat sink. The combination of the plurality of amplifier stage power ratings yields a total power rating greater than the heat sink power rating.
The plurality of amplifier stages includes a first amplifier stage and a second amplifier stage. The heat sink has a power rating of 50 watts while the first amplifier stage and the second amplifier stage each have a power rating of 50 watts.
Power is provided from the amplifier assembly by adjusting the power level of the first amplifier stage and the second amplifier stage such that the total resulting power level of the combination of the first amplifier stage and the second amplifier stage is less than the heat sink power rating.
The amplifier assembly can be formed as part of an alarm system that includes a plurality of alarms. The alarm system includes a plurality of detector loops, each detector loop having at least one alarm or detector. Each detector loop is located within in a zone.
As part of the alarm system, the amplifier assembly provides backup audio power to the alarm system. The alarm system includes an amplifier assembly connected to a plurality of alarms located in a plurality of zones. At least one of the amplifier stages in the amplifier assembly powers an audio signal for the plurality of alarms. When an amplifier stage power failure is detected, the power source is switched from the first of a plurality of amplifier stages to a second amplifier stage. The audio signal is thereby powered for the plurality of alarms using the second amplifier stage.